JP2782605B2 - Automatic control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an automatic control device for controlling a power conversion circuit used as a motor drive device, and more particularly to an automatic control device using a proportional integral amplifier having an integral amplifier with an output limiter. It is about.

[Conventional technology]

The motor drive device shown in FIG. 3 is commonly used.

FIG. 3 shows an example of a DC motor driving device for performing speed control, 1 is a speed setting device, 2 is a speed control circuit, 3 is a current control circuit, 4 is a power conversion circuit, 5 is an output current detector, and 6 is an output current detector. An electric motor, 7 is a speed detector, and 8 is a load machine. Here, 21 and 31 are adders, and 22 and 32 are amplifiers.

That is, the operation of such a configuration is well known as having a speed control feedback loop outside the current control loop. The output difference between the speed setter 1 and the speed detector 7 is amplified by the speed control circuit 2 so that the current setting signal Is given to the current control circuit 3. Here, in the case of a DC motor driving device, this current setting signal is also a torque command.

Further, the difference between the current setting signal and the output current detector 5 is amplified by the current control circuit 3 and sent to the power conversion circuit 4 so that the output current of the power conversion circuit 4 is controlled to be the same as the current setting signal. The power conversion circuit 4 drives the electric motor 6 to operate the load machine 8.

Next, the control characteristics of the apparatus shown in FIG. 3 are shown using transfer functions as shown in FIG.

In FIG. 4, reference numeral 200 denotes a speed control circuit, 400 denotes a torque generator, 601 denotes an adder, and 602 denotes a control target.

That is, ω ^* is a speed setting and corresponds to the output of the speed setting device 1, and τ ^* is a torque command and corresponds to the output of the speed control circuit 2 shown in FIG. τ is the torque of the motor 6,
τ _L indicates the load torque of the load machine 8 and ω indicates the rotation speed of the electric motor 6.

In the speed control circuit 200, the adder 201 corresponds to the adder 21, amplifier 22, linear amplifier 202 having a gain K _P, limits the integrating amplifier 203 and integrating amplifier 203 outputs the integration time K _I limiter circuit 204 , An adder 205 that adds the output of the proportional amplifier 202 and the output of the limiter circuit 204, and an output limiter circuit 206 that performs a limiter operation of the amplifier 22. The output of the speed control circuit 200 is, of course, the torque command τ ^* .

Further, the current control circuit 3, consider the power conversion circuit 4 and the motor 6 as an ideal torque generator, illustrated as a torque generator 400 having a gain (torque generation coefficient) K _T, the torque generator 400 output torque τ It is.

This torque τ gives the load machine 8 a load torque τ _L ,
From the viscous resistance τ _D of the electric motor 6 and the load machine 8,
To accelerate the motor at acceleration torque tau _A. That is, (τ =
τ _L + τ _A + τ _D ).

Further, the adder 601 obtains (τ _A + τ _D ) by subtracting the load torque τ _L from the torque τ to obtain the rotation of the electric motor 6. The rotation speed ω of the electric motor 6 is obtained by calculating the integrated value of the acceleration torque τ _A and the electric motor GD ² , J.

This is as follows from an open loop gain with respect to the speed setting ω ^* of the rotation speed ω, ignoring the limiter function of the speed control circuit 200.

In equation (1), even if the denominator is a quadratic equation and stability is not guaranteed, setting [K _P K _I (J / D)] here gives the first-order lag equation, And the response to the speed setting ω ^* of the rotation speed ω including the feedback loop is [ω = 1 / (1 + S / K) ω ^* ].
It becomes stable.

[Problems to be solved by the invention]

However, the above-mentioned stabilization is limited only when the speed control circuit is saturated or when each signal is not applied to the limiter circuit 204 and the output limiter circuit 206 shown in FIG. This will be described with reference to FIGS. 5 and 6.

Figure 5 shows a case not applied to the limiter, (a) shows the time course of the speed setting omega ^* and the rotation number ω, (b) speed control circuit 200 outputs a torque command tau ^* signal P of the proportional amplifier 202 outputs _A and the output of the integrating amplifier 203 are added to the limiter circuit 204
Shows the time course of the signal I _A that has passed through the.

That is, as shown as a speed response without a limiter, in the case of the above-mentioned response of [ω = 1 / (1 + S / K) ω ^* ], no overshoot occurs in the speed response of the motor. That is, the signal P _A also signals I _A also exponentially converge, when the rotation speed omega is converged to the speed setting omega ^* is to maintain the convergence value is just the rotation number omega signals I _A to the speed setting omega ^* This is a value corresponding to a required value (τ _L + D).

Next, FIG. 6 shows a case where the output of the integrating amplifier shown in FIG. 5 is applied to a limiter, and _VL is a limit value of the limiter circuit 204 and the output limiter circuit 206. here,
_A portion of the signal IA represented by a thin line indicates a change when it is assumed that the limiter circuit 204 is not provided.

That is, the speed setting omega ^* greatly changes at time T _10, takes the limit value V _L of the output limiter circuit 204, the torque command tau ^* does not change any more. Therefore, the torque generator 400 outputs a constant torque, and the electric motor 6 and the load machine 8 accelerate almost constantly. Integrating amplifier at time T ₁₁ 203
This indicates that the output also depends on the control value _VL of the limiter circuit 204.

To reach finally a time T ₁₂ rotational speed omega speed set in omega ^*, this time T ₁₂ integrating amplifier 203 outputs the rotation number omega is lower than the speed setting omega ^* in front does not decrease, the signal I _A limit value V _L
Remains. Thus even though the rotation speed omega speed setting omega ^* and matches, ^* signal I _A and the torque command τ has a limit value V _L which is determined by the limiter circuit 204 and an output limiter circuit 206.

Limit V _L has a large value far from the load torque tau _L and viscosity resistance tau _D. Therefore, the torque generator 40
0 generates a torque τ larger than the load torque τ _L and the viscous resistance τ _D according to the torque command τ ^* , and the electric motor and the like are further accelerated. That is, an overshoot occurs in the motor speed. This overshoot causes the output of the integrating amplifier 203 to become equal to the load torque τ due to the speed overshoot.
Until reduced to a value corresponding to the _L and the viscosity resistance tau _D.

As described above, in the method using the method based on the simple speed control feedback loop, the overshoot of the speed due to the limiter portion of the control circuit and the saturation of the signal cannot be avoided.

[Means and actions to solve the problem]

In view of the above, the present invention makes the limiter circuit limit value for the output of the integrating amplifier in the speed control circuit particularly variable, estimates the load torque from the torque command and the rotation speed, and sets the load torque viscous resistance to A limiter circuit limit value corresponding to the torque required for maintaining the speed is obtained.

More specifically, the estimated value of the torque generated by the torque generator is obtained from the torque command (τ ^* ) to the torque generator and the estimated torque generation coefficient ( _T ) of the torque generator. From the change in the rotational speed (ω) and the inertia GD ² , J of the motor and load machine , More load torque and estimated torque due to viscous resistance Ask for this Is converted into a torque command value (τ _LD ^* ) to obtain the limit value of the output of the integrating amplifier in the speed control circuit.

As described above, by always setting the limit value of the limiter circuit of the integrating amplifier in accordance with the load torque and the viscous resistance, the motor is accelerated while the torque command is applied to the limiter of the output limiter circuit in the speed control circuit. Also in this case, the output of the speed control circuit is set to a torque command corresponding to the load torque and the viscous resistance, that is, a torque command necessary to maintain the rotation speed. Therefore, the motor does not accelerate any further, and can converge favorably to the same rotational speed as the speed setting.

 Further, the present invention will be described in detail with reference to the accompanying drawings.

〔Example〕

FIG. 1 shows an embodiment of the present invention shown in FIG. 4, wherein 200 'is a speed control circuit, 901 is a generated torque estimation circuit, 902 is an acceleration torque estimation circuit, 903 is an adder, 904
Is a conversion circuit for converting (torque / torque command).

That is, the generated torque estimating circuit 901 outputs the torque command τ ^*
Estimated torque generated by the torque generator using the estimated torque generation coefficient _T of the torque generator 400 as a gain Is output. An acceleration torque estimating circuit 902 calculates an estimated acceleration torque contributing to acceleration based on the estimated values of the inertia GD ² and J of the electric motor 6 and the load machine 8. And specifically, a differentiation circuit for the rotational speed ω.

An adder 903 obtains a difference between the estimated generated torque and the estimated acceleration torque. That is, the output of the adder 903 is an estimated value of the load torque τ _L and the viscous resistance τ _D Becomes The conversion circuit 904 uses the reciprocal of the gain of the generated torque estimation circuit 901 as its gain, and Output the torque command value τ _LD ^* corresponding to.

On the other hand, the speed control circuit 200 'has a limiter circuit 204' as a limiter for the output of the integrating amplifier 203. This limiter circuit 204 'can vary its limit value exceptionally, and the limit value is the torque command value τ ^{* of the} output of the conversion circuit 904 ^.
_{This is} set by the _LD . FIG. 2 shows the speed response of such a configuration.

In Figure 2, tau ^* _LD is' a limit value of the signal I _A 'limiter circuit 204 which is set by the converter 904 output is a limiter circuit 204' output.

Now speed setting omega ^* greatly changes at time T _20, the torque setting tau ^* takes the limit value V _L of the output limiter circuit 206, the limit value of the limiter circuit 204 'at shortly integrating amplifier 203 output is also time 21 tau ^* It takes _LD .

The proportional signal P _A of the amplifier output (V _L -τ ^* _LD) between greater than a torque command tau ^* limit value V _L, therefore, the torque generator 400 is constant torque generated corresponding to the limit value V _L , The electric motor 6 and the load machine 8 accelerate at a substantially constant acceleration.

Before long, the rotational speed ω is small signal P _A approaches the speed setting ω ^* at time T _22, when it comes to _{(V L> P A + τ} * LD),
It decreases with the change of the torque command tau ^* signals P _A, time T
_{At 23, the} rotational speed ω matches the speed setting ω ^* .

As for the time point 23, the signal P _A of the proportional amplifier 202 output is zero, the speed control circuit 200 ^'* torque command output τ the integration amplifier 203 and the limiter circuit 204' a signal I _A 'of the output of the ing. The output of the limiter circuit 204 'is limited to τ ^* _LD of the output of the conversion circuit 904, and therefore the output of the speed control circuit 200' is also τ ^* _LD . The tau ^* _LD is a value obtained by estimating the viscous resistance of the as the load torque tau _L and the motor 6 and the load machine 8 described above,
When the torque generator 400 outputs a torque corresponding to τ ^* _LD , the motor is in a state of maintaining a constant speed. That time T ₂₃ later, the motor overshoot becomes constant speed does not occur.

〔The invention's effect〕

As described above in detail, according to the present invention, the output of the integrating amplifier in the speed control circuit is constantly changed so as to limit the output to a value corresponding to the load torque and the viscous resistance. It is possible to provide a special device capable of realizing a motor drive device that solves the above problem.

Although the description has been made in the case where the speed control is performed by the DC motor driving device, the present invention is naturally applied to the AC motor driving device and other control methods. Furthermore, the circuit configuration is used for convenience of description, but it goes without saying that the gist of the present invention is effective even if it is performed by software using a microcomputer.

[Brief description of the drawings]

FIGS. 1 and 2 are a system diagram and a speed response diagram, respectively, showing a main configuration of an embodiment of the present invention. FIGS. 3 and 4 show a conventional DC motor driving device for performing speed control. FIG. 3 is a configuration diagram and a control characteristic diagram thereof. 5 and 6 are time transition diagrams showing a case where the limiter is not applied and a case where the limiter is applied, which is shown for the purpose of explaining FIG. 2,200,200 '... speed control circuit, 6 ... motor, 8 ...
Load machine, 400 torque generator, 901 generated torque estimation circuit, 902 acceleration torque estimation circuit, 904 conversion circuit, ω ^*: speed setting, ω: rotation speed, τ ^*: torque command, tau ...... torque, tau _{L ......} load torque, tau _{A ......} acceleration torque, tau _{D ......} viscosity _{resistance, P A, I A, I} A '...... signals,
V _L , τ ^* _LD …… Limit value.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-78806 (JP, A) JP-A-3-100802 (JP, A) JP-A-2-101981 (JP, A) JP-A-1- 218389 (JP, A) JP-A-64-97188 (JP, A) JP-A-63-274385 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H02P 5/00 G05D 3 / 00 G05B 13/02 G05B 11/42

Claims (1)

(57) [Claims] 1. An automatic control device having a proportional-integral amplifier for amplifying a deviation between a set value and a feedback value of a control target, and configured to send an output of the proportional-integral amplifier to a power conversion circuit as a torque command. The specified value of the generated torque of the motor from the torque command Estimated value of acceleration torque from motor and motor speed And the difference An automatic control device, comprising: an operational amplifier for obtaining an estimated value of a load torque, and wherein the estimated value of the load torque is configured to be a limit value of an output limiter of an integrating amplifier included in the proportional-integrated amplifier.